Influence of defects on the electrical and optical characteristics of blue light-emitting diodes based on III–V nitrides

We have measured the electrical and optical properties of blue light-emitting diodes (LEDs) based on III–V nitrides. The current–voltage characteristic is described by means of the relation I=I0 exp(αV). In this equation α is temperature independent, suggesting a process of conduction by tunneling, as was recently reported also for blue-green LEDs based on III–V nitrides [Appl. Phys. Lett. 68, 2867 (1996)]. We explain the differences between blue and blue-green devices taking into account the tunneling process across semiconductor interfaces, in which a great number of defects is present. The light output intensity of the LED as a function of junction–voltage data reveals a dependence on the junction–voltage of the type L=L0 exp(qV/1.4 KT), indicating that the radiative recombination path is via deep levels located at the forbidden gap. Furthermore, we find that the light output–current characteristic follows a power law like L∝Ip. From the analysis of data it appears that, contrary to expectations, the n...